btrfs-progs: limit minimal num of args for btrfs-image

The btrfs-image requires at least 2 args to run,
one for the source dev/file, the other for the target dev/file.

This patch depends on patch:
	btrfs-progs: move the check_argc_* functions into utils.c

Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

btrfs-image.c

@@ -2522,6 +2522,10 @@ int main(int argc, char *argv[])
 	}
 
 	argc = argc - optind;
+	set_argv0(argv);
+	if (check_argc_min(argc, 2))
+		print_usage();
+
 	dev_cnt = argc - 1;
 
 	if (create) {